1. Field of the Invention
The present invention relates to an integrated electronic device provided with a plurality of passive components such as inductors. The present invention also relates to a method of manufacturing such an integrated electronic device.
2. Description of the Related Art
An RF (radio frequency) system or RF circuitry incorporated in e.g. a mobile terminal generally includes an IPD (integrated passive device) functioning as high-frequency module devices in order to achieve high performance, small size, light weight, etc. An IPD incorporates passive components such as inductors, capacitors, resistors and filters. Among these components, inductors tend to have a lower Q factor (quality factor) than e.g. capacitors. When an IPD includes an inductor, the entire IPD is also likely to have a low Q factor. Therefore, there are demands for IPDs with high Q factor. Further, since RF systems have utilized higher frequency bands, IPDs are also required to adapt to those higher frequency bands. These and other technological aspects about the IPDs are disclosed in the following Patent Documents 1 and 2, as well as Non-Patent Documents 1 and 2.
Patent Document 1: JP-A-H04-61264.
Patent Document 2: U.S. Pat. No. 5,370,766.                Non-Patent Document 1: Albert Sutono et al., “IEEE TRANSACTION ON ADVANCED PACKAGING”, VOL. 22, No. 3, AUGUST 1999, p. 326-331.        Non-Patent Document 2: Guo Lihui et al., “IEEE ELECTRON DEVICE LETTERS” VOL. 23, No. 8, AUGUST 2002, p. 470-472.        
Non-Patent Document 1, for example, teaches an IPD manufactured by LTCC (low-temperature co-fired ceramic) technology. Such an IPD manufactured by LTCC technology includes a multi-layered ceramic substrate, provided with a plurality of passive components. In some cases, a plurality of coils are stacked over a plurality of layers in the multi-layered ceramic substrate in order to increase inductance of an inductor. Such a configuration is suitable for increasing the Q factor of the entire IPD because the higher inductance an inductor has, the higher Q factor the inductor tends to have.
Such an IPD manufactured by LTCC technology, however, faces the following drawbacks. Each of the coils in the inductor is surrounded by ceramic, which has a relatively large dielectric constant. Thereby, the inductor is unduly affected by a parasitic capacitance. A large parasitic capacitance affecting the inductor prevents enhancement of the Q factor of the inductor. Accordingly, IPDs manufactured by LTCC do not show a sufficient Q factor in many cases.
Further, a Q factor is frequency dependent in general. The larger the parasitic capacitance is, the more the self-resonant frequency of the inductor and the peak frequency of the Q factor of the inductor shift toward the low frequency side, whereby the high-frequency characteristics of the IPD is deteriorated. Thus, due to the insufficient Q factor, IPDs manufactured by LTCC technology are sometimes prevented from applying to a targeted high-frequency band and achieving a favorable high-frequency characteristic.